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| Home > Publications database > Stammapplikation von Imidacloprid bei Orangenbäumen unter Berücksichtigung der Wirkstoff-Formulierung und der Wasserversorgung der Pflanzen |
| Book/Report | FZJ-2019-04518 |
1988
Forschungszentrum Jülich, Zentralbibliothek, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/22631
Report No.: Juel-3591
Abstract: Experiments on the trunk application of the inseeticide imidacloprid to fruit trees have been performed at the Institute of Radioagronomy since 1993. The present work is concerned with the uptake, plant-internal distribution and biological effects of imidacloprid applied to the hark of Citrus sinensis (L.) OSBECK. The effects of the active ingredient formulation and the water supply to the trees were also studied. To begin with, basic insights were gathered in a large-scale experiment with two-year-old trees of the cv. Newhall on Citrange Carrizo rootstocks under environmentally controlled conditions. A field study was then performed in the subtropical north of the Republic of South Africa with nine-year-old Valencia orange trees of the cv. Delta on Poncirus trifoliata (L.) RAF. rootstocks to improve this method for practical application. In both experiments [pyridinyl-$^{14}$C-methylene]imidacloprid was applied in form of Confidor$^{\circledR}$200 SL (20 % a .i.) or an AL 100 (10 % a.i.). In the growth-chamber experiment, two-year-old orange trees were cultivated in pots and watered daily to the same weight until a soil moisture of 8 or 20 vol.% had been reached. At a soil moisture of 20 vol.% the transpiration losses from the orange trees of 421 ± 18 g H$_{2}$O d$^{-1}$ were twice as high as these from the 8 vol.% soil moisture variant with 223 ± 14 g H$_{2}$O d$^{-1}$ (n=8). Under these conditions, 6 mg a.i. (=1.8 MBq) was applied in form of Confidor$^{\circledR}$200 SL or AL 100/1 to a trunk surface of about 16 cm$^{2}$ below the bud union. After 30 days, on average (n=8) about 55 % of the radioactivity applied in form of AL 100/1 was detected within the trees and about 19 % after the application of Confidor$^{\circledR}$200 SL. At the same time the remaining radioactivity was washedoff the bark surfaces using a water/acetone solution. lt still represented 90 % [$^{14}$C]imidacloprid so that throughout the experimental period unchanged active ingredient for penetration of the bark predominantly was available. The formulation had a significant (P=0.05) influence on imidacloprid uptake but irrigation did not. Just a few hours after the trunk treatment with [$^{14}$C]imidacloprid, it was possible to detect radioactivity in the leaves of the two-year-old orange trees. Over a period of 30 days, the transport rates for $^{14}$C-labelled substances were always higher after the application of AL 100/1. On the 30th day, for this preparation approx. 20 % of the applied radioactivity was recovered in the leaf blades, whereas this was significantly less by a factor of 10 after treatment with Confidor$^{\circledR}$200 SL. However, the influence of irrigation was not significant (P=0.05). The active ingredient was distributed acropetally with the water stream inside the trees and accumulated in the leaf bladesand in the stipules. Macroautoradiograms indicated a uniform distribution of $^{14}$C in the intercostal region. In a supplementary experiment, microautoradiograms confirmed the long-distance transport of imidacloprid in the xylem. In the field experiment, 2 g a.i. was applied in form of Confidor$^{®}$200 SL or 1 g a.i. as AL 100/2 to nine-year-old orange trees an a trunk area of about 700 cm$^{2}$ above the bud union at the time of the second sprouting in November 1996. Three weeks before starting the experiment, the water supply had been cut off to half of the trees. In this experiment, from six weeks after hark application the Confidor$^{®}$200 SL permitted perceptibly higher, and up to the 15th week persistent, inputs of imidacloprid into the leaves in comparison to AL 100/2. Until the 15th week, in the group of trees with water supply, 10.3 ± 0.6 % of the applied radioactivity (n=3) from Confidor$^{\circledR}$200 SL was transported into the leaves. These values were even exceeded twofold for orangetrees grown without watering. After applying AL 100/2, 5.9 ± 2.6 % was recorded in leaves of the trees in the moist group and 6.9 ± 2.3 % in the dry variant. In parallel, dry stress symptoms (low sap-flow rates, relative water contents of the leaves and fruit sizes etc.), even including leaf curling in the 12th week, occurred for the trees with decreasing soil moisture. The foliage weights of the orange trees were approximately equal in the 15th week, amounting to 4.25 ± 0.65 kg dry weight (n=12). Compared to the leaf blades the active ingredient equivalent concentrations in the dry matter of the fruits were lower by a factor of about 20 - 30. In the fruits $^{14}$C-labelled substances were largely accumulated in the flavedo, partly in the oil glands. In general, the suberized cell layers of the periderm form the penetration barrier for trunk-applied imidacloprid. The formulation has a perceptible influence on the uptake of active ingredient. Higher solvent concentrations in the preparation bring about higher inputs of active ingredient in the skort term but may also cause phytotoxic reactions. The 200 SL formulation permitted a sustained subsequent delivery of imidacloprid in the humid and warm climatic conditions of the South African summer, although active ingredient crystallized out in the application coating just a few hours after trunk treatment. The new shoots are preferentially supplied with imidacloprid. This was also confirmed in the field experiment by the results of an estimate of important citrus pests, where, for example, imidacloprid concentrations of 0.4 $\mu$g g$^{-1}$ dry matter were suffizient to control Toxoptera citricidus (KIRKALDY).
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